highest level;  high-water mark
 lowest level;  minimum level;  ground floor
 spirit level;  level;  leveling instrument;  levelling instrument
 significance level;  level of significance;  critical p-value
 leveling instrument;  levelling instrument;  surveyor's level
 level of awakeness;  level of arousal
 benchmark (surveying);  bench mark
 document architecture level
 primary benchmark (surveying);  fundamental benchmark